U.S. Geological Survey

Hydro-Climatic Data Network (HCDN):
Streamflow Data Set, 1874 - 1988

By J.R. Slack, Alan M. Lumb, and Jurate Maciunas Landwehr

USGS Water-Resources Investigations Report 93-4076

The potential consequences of climate change to
continental water resources are of great concern in the management
of those resources. Critically important to society is what
effect fluctuations in the prevailing climate may have on
hydrologic conditions, such as the occurrence and magnitude of
floods or droughts and the seasonal distribution of water supplies
within a region. Records of streamflow that are unaffected by
artificial diversions, storage, or other works of man in or on the
natural stream channels or in the watershed can provide an account
of hydrologic responses to fluctuations in climate. By examining
such records given known past meteorologic conditions, we can
better understand hydrologic responses to those conditions and
anticipate the effects of postulated changes in current climate
regimes. Furthermore, patterns in streamflow records can indicate
when a change in the prevailing climate regime may have occurred
in the past, even in the absence of concurrent meteorologic
records.

A streamflow data set, which is specifically suitable for the
study of surface-water conditions throughout the United States
under fluctuations in the prevailing climatic conditions, has been
developed. This data set, called the Hydro-Climatic Data Network,
or HCDN, consists of streamflow records for 1,659 sites throughout
United States and its Territories. Records cumulatively span the
period 1874 through 1988, inclusive, and represent a total of
73,231 water years of information.

Development of the HCDN Data Set: Records for the HCDN were
obtained through a comprehensive search of the extensive surface-
water data holdings of the U.S. Geological Survey (USGS), which
are contained in the USGS National Water Storage and Retrieval
System (WATSTORE). All streamflow discharge records in WATSTORE
through September 30, 1988, were examined for inclusion in the
HCDN in accordance with strictly defined criteria of measurement
accuracy and natural conditions. No reconstructed records of
"natural flow" were permitted, nor was any record extended or had
missing values "filled in" using computational algorithms. If the
streamflow at a station was judged to be free of controls for only
a part of the entire period of record that is available for the
station, then only that part was included in the HCDN, but only if
it was of sufficient length (generally 20 years) to warrant
inclusion. In addition to the daily mean discharge values,
complete station identification information and basin
characteristics were retrieved from WATSTORE for inclusion in the
HCDN. Statistical characteristics, including the monthly mean
discharge, as well as the annual mean, minimum and maximum
discharge values, were derived for the records in the HCDN data
set. For a full description of the development and content of the
Hydro-Climatic Data Network, please take a look at the
HCDN Report.

The United States was divided and sub-divided into successively
smaller hydrologic units. The first level of classification
divides the U.S. into 21 water-resources regions. For a more
comprehensive explanation of the hydrologic units refer to
hucs.html.
HCDN data for a specific region can be obtained by selecting the
corresponding region on the map or from the list below.

The gray lines are state lines, the blue lines are major rivers, and the white
lines are water-resources region boundary lines.

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